Defrosting refrigeration system



June 1932- v. P. WARREN DEFROSTING REFRI GERATI ON SYSTEM ZSheets-Sheet 1 Filed Jan. 19, 1931 mm .H Q

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June M, 1932. v. P. WARREN DEFROSTING REFRIGERATION SYSTEM Filed Jan. 19, 1931 2. Sheets-Sheet 2 Patented June 14, 1932 VIRGIL P. WARREN, F ATLANTA, GEORGIA DEFBOSTING REFRIGERATION SYSTEH Application filed January 19, 1981. Serial No. 509,809.

This invention which is a continuation in part of my application Serial No.445,371,filed April 18, 1930, now matured into Patent No. 1,827,410, relates to mechanical refrigeration and particularl ,although not exclusively, to show case re rigeration.

The general object of the invention provides means and amethod for defrosting the refrigerating coils and for preventing the water which eventuates from the defrosting collecting and freezing at any undesired point in the refrigeration apparatus.

A more specific object of the invention is the provision of a refrigerating system of the Carnot cycle type modified by means which can be periodically manipulated to cause the circulation of the hot compressed gaseous refrigerant through the refrigerating coils and through other conduits disposed in advan- 29 tageous positions to prevent the freezing of the drainage from the defrosting operation.

A further object of the invention is to provide a valve controlled conduit connected into the refrigeration circulation system in.

such a manner that the circulation of refrigerating medium may be made to by-pass the condenser, said conduit extending from the compression end of the compressor, first into heat exchanging relationship with admin- 30 age conduit arranged below the coil, and then communicating with the coil whereby the hot compressed refrigerating medium will be circulated, first in proximity to the drainage conduit and tlienthrough the coil, maintaining the drainage conduit sufiiciently warm during the defrosting period to prevent clogging of the drain by freezing of the moisture defrosted from the coil and which would result in an over-flow of said moisture into the chamber of the show case.

Another object of the invention is the construction of the pan or enclosure which houses the refrigerating coils and defines the circulation of air about said coils and within the show case, particularly in its cooperative relation to the defrosting system whereby the metal of the pan at the lower-most part and adjacent the drain, is made to contact intimately with the defrosting conduit.

60 Other objects of the invention will appear as the following description of a preferred embodiment thereof proceeds.

Before referring to the drawings, it ma be said that with the advent of the quic freezing process of meats, fish, poultry and fruits, a problem arises of furmshing show cases capable of maintaining a very low temperature, for example, from fifteen to twenty degrees F. At this low temperature, the coils will collect frost and ice very rapidly, and consequently, must be defrosted, since a heavily frosted coil is quite inefficient in its heat exchanging capacity, the encrusted ice acting as a heat insulation.

The usual procedure in defrosting a coil is to cut off the refrigeration, open up the show case, and allow the atmospheric temperature to heat the coil to a temperature above freezing in order for the ice to melt. This generally requires several hours, in which time the contents of the case become heated up, a condition which would be inimical to the proper preservation of meats frozen by the new quick-freeze process. Consequently, one of the conditions upon which the salability of quick-frozen products de pends is that the temperature of the product shall never rise above the freezing point.

The present invention overcomes this difficulty by providing an entirely new system of defrosting which does not require that the show case be opened up at all and which takes but a few minutes to accomplish as compared with hours in the known method.

In the drawings which illustrate the present invention and in which the same characters of reference are used throughout the several figures to denote identical parts:

Figure 1 is a diagrammatic view showing a Carnot cycle type refrigeration system in conjunction with the elements constituting the defrosting system;

Figure 2 is a cross-section of the show case unit including the air circulating pan;-

Figure 3 is a horizontal section through either of the three-way valves shown in Figure 1;

Figure 4 is a detailed view in vertical section showing the contact between the metal rtions of the pan and the associated deosting conduit; Figure 5 is a section taken along the line 5-5 of Figure 2;

pansion valve 6 beyond which, the liquefied refrigerant is permitted to expand into the coil 7, the expansion being attended by absorption of heat from the air surrounding the coil'7, the latter performing its refrigerating function in usual and known manner.

Since the present invention is particularly adapted for show case use, the several convolutions of the refrigerating coil 7 are shown in Figure 2 suspended from the top wall of a showcase. The refrigerating unit herein illustrated operates on the so called dry system.

. In Figure 1, the several convolutions of the coil 7 are shown as passin through a plurality of heat dissipating p ates or fins 8. The spent, expanded and somewhat heated gaseous refrigerant returns from the coil 7 by way of the conduit 9, back to the suction side of the compressor where it is again compressed, .the refrigerating cycle being thus repeated.

Although the invention is particularly adapted to a dry coil system of refrigeration, there is nothing inherent in its defrosting principle that bars it from application to any system in which a supply of heated aseous refrigerant is available as the deosting medium.

The concept of the present invention, broadly stated is, for the purpose of defrosting, to by-pass the heated compressed gaseous refrigerant in the conduit 2 around the condenser so that it will not be cooled and liquefied and to admit it in heated state to the refrigerating coil substituting the same temporarily for the cold expanding refrigerant. In order to carry out the principle embraced in this concept, a pair of three-way valves 10 and 11 are provided, one being intercalated in the hot compressed gas conduit 2, between the compressor and condenser, and the other being interposed in the refrigerating unit between the expansion valve 6 and the coil 7. These valves may be of similar construction, and there is nothing inherently new in their construction, per se. The-crosssection shown in Figure 3 is that of either of the three-way valves. For example, valve 10 shows that in one position of the valve the conduit 2 is 0 en to the condenser, while 1n another position of the valve, the conduit 2 is occluded with respect to the condenser, but open with regard to the by-pass pipe 12. The valve 11 in one position opens the expansion valve to the coil 7, while in another pos1t1on the expansion valve is closed, the (301i 7 being open to the by-pass.

Assuming that the refrigerating cycle has operated for a number of hours and that a layer of frost has'condensed upon the coil 7, the operator merely turns the valves 10 and 11 so that each is in position indicated in Figure 3, closing the system to the condenser and expansion valve and opening it to the by-pass. The compressor then pumps the heated gaseous refrigerant through said bypass and directly into the coil 7, heating it and condensing the frost in-crustation. At the temperature of the compressed gaseous refrigerant this defrosting takes but little time, ordinarily from five to' fifteen minutes according to the thickness of the frost layer. There is not time for any appreciable rise in the temperature of the atmosphere within the show case.

It has been found that due to the additional coil volume represented by the coil 25, which the refrigerant is required to occupy when used as a heating medium and the temperature drop which it undergoes in performing its heatlng function, the refrigerant would return to the compressor with an attenuated density so as to cause a decided drop in the compression pressure, that is to say, in the work done by the compressor. This would diminish the heat output of the compressor and consequently, reduce the heating efficiency of the circulating refrigerant.

This drop in the compression pressure is avoided by lacing a throttling orifice in the suction con uit 9 so as to retard the return of the refrigerant and thus to maintain a pressure back of the orifice and clear back to the compression. end of the compressor. The size of this orifice is of courseselected to maintain a compression pressure that shall produce the desired heat value in the compressed refrigerant. It is readily understood that the suction conduit must be unobstructed during the normal refri eration cycle, consequently, the orifice is est provided as a bleed passage 41 in a valve 42, the latter being an element of the valve unit 43, which is intercalated in the suction conduit.

When the system is working in its refrigerating capacity, the valve is opened wide so as to permit unimpeded flow back to the compressor, but when the system is functioning as a heater the valve is closed compelling the refrigerant to flow through the bleed passage.

In testing out the invention it has been found that after running the hot gaseous refrigerant through the coil .7 in defrosting the coil, the atmosphere in the top of the show case did not ,rise more than five degrees, while in the bottom of the show case no rise was perceptible. The maintenance of the low temperature in the show case while the defrostin is going on is due to the factthat the de rosting takes place from the inside, and that while any frost at all remains on the coil 7, it acts as a heat insulation preventing the heat from the defrosting fluld being dissipated in the show case until the last vestige of frost is gone.

As the three-way valves are then turned to restore the refrigerating operation, this recommences immediately and a little more vigorously than normally, since the expansion valve has been heated due to its prox imity to the course of the defrosting fluid so,

that expansion takes place at the start more vigorously.

Referring now to Figure 2, it will be noted that the coil 7 is suspended from the top of the show case in any suitable manner as for instance, between screw eyes 13 through the eyes of which is assed a rod 14 extending beneath a layer of the coils and between certain of the fins 8. There may be one of these suspending rods at each end of the coil or a plurality of the same, depending of course upon the length of the coil within the show case. The coil is preferably housed within a pan 15. Said pan is preferably of laminated construction as shown having inner and outer walls 37 and 38 of metal and a sheet 39 of asbestos or other insulation material between, the idea being to conserve the refrigerating temperature within said pan and about the convolutions of said coil so as to improve the circulation of air which courses through the show case and into and out of contact with the refrigerating unit. In order to determine a uniform circulation of refrigerated air in all parts of the show case, the pan 15 is constructed to operate according to the so called two-cycle principle. That is to say, two similar air eddies are maintained, one at the front and one at the back of the show case. This type of air circulation is produced by the pan having an elongated slot or opening 16 at its-lower-most portion, in the middle, said slot being roofed by a bridge 36, the same being also of laminated construction having inner and outer metal layers and an intermediate heat insulating layer, and being spaced at its sides from the pan forming cold air ports 17 and 18.

It will be noted that the pan does not extend clear to the top wall 8 of the show case but terminates at a distance below it, as shown at 19 and 20, the space above, between said pan and show case affording an inlet at each side, for the current of relatively warm air to flow in to the refrigerating unit. The fins 8 are arranged cross-wise as shown so as to oppose minimum obstruction to the entrance of the air. The circulation of air is as follows Relatively warm air rises along the front and back walls. of the show case, enters the inlets at the sides of the pan 15 flows over the convolutions of the refrigerating coil 7, descends by gravity within the panand issues through the ports 17 and 18, flowing through the slot 16 down upon the products which are to be maintained below freezing point.

The pan as shown in the illustration has upturned ends 21 and 22 constituting'sides of the slot 16 and forming gutters 23 from which lead drain pipes 24 which extend outside of the show case.

One of the defects of defrosting as ordinarily practiced is that the water eventuat ing from the melting of the frost runs down upon the meats or other products in the show case. In a defrostin system as the present invention contemp ates, and particularly in the use of a pan of the type as illustrated and described, unless specific means are provided to prevent it the water resulting from the defrosting freezes in the gutters 18 and in the drain pipes 24 stopping upthe latter and preventing their proper functioning so that there is an overflow of the water on to the frozen products.

The present invention obviates this difliculty b extending the by-pass conduit 12 which y-passes the condenser and expansion valve in the form of a loop or coil 25 extending along the sides of the slot 16 and in heat exchanging relation thereto. In order to extend the conduction of heat from the coil 25 as far as possible with regard to the adjacent portions of the pan 15, the coil 25 is laid in the angles formed by the upturned ends 21 and 22, in intimate contact with the inner metal surfaces thereof, and separate metallic channel members placed over said coils preferably in intimate contact therewith at one side and top, the other sides of said channel members being in contact with the outer metallic walls of the pan 15, heat from said coil thus being conducted through the inner and outer walls of the pan to the drain pipes 24. It thus becomes impossible for ice to accumulate in the gutters 23 and drain pipes 24, since the regions of these parts are heated to at least the same extent as the convolutions of the coil 7.

It is to be understood that in the defrosting system of the present invention, no liquid refrigerant ever passes into'the coil 25 and substantially little or none in the coil 7, as only the heated compressed gases make this circuit and any gas that is condensed in the coil 7 is drawn back through the suction line and compressed and reheated by the action of the compressor in the regular way closed what I believe to be a preferred and practical form of my invention, it is to be understood that the changes in the detailed construction or arrangement of the several parts can be contemplated without transcending the scope of the invention as clalmed.

What I claim is:

1. Defrosting refrigeration circulation system including a compressor and a refrigerating coil, drainage means underlylng said coil, said circulation s stem being divided into parallel branches etween the pressure side of said compressor and said coil, one of said branches having a ortion arranged in heat exchanging relation to said drainage means, means for selectively determining the path of flow of said refrigerant through one or the other of said branches, and means for compensating the drop in compression pressure incident to the functioning of said refrigerant as a heating medium of said coil and drainage means, for maintaining the heating efliciency of said compressor during the heating period.

2. Defrosting refrigeration circulation system including a compressor and a refrigeratin coil, drainage means underlying said 0011, said circulation system being divided into parallel branches between the pressure side of said compressor and said coil, one of said branches having a portion arranged in heat exchanging relation to said drainage means, means for selectively determining the path of flow of said refrigerant through one or the other of said branches, and throttling means in said circulation system on the suction side of said compressor for building up a back pressure on the pressure side of said compressor to compensate the drop in com pression pressure incident to the functioning of said refrigerant as a heating medium of said coil and drainage means, for maintaining the heating efliciency of said compressor during the heating period.

3. Defrosting refrigeration circulation system including a compressor and a refrigerating coil, drainage means underlying said coil, said circulationsystem'being divided into parallel branches between the pressure side of said compressor and said coil, one of said branches having a portion arranged in heat exchanging relation to said drainage means,

(35 means for selectively determining the path of flow of said refrigerant through one or the other of said branches, and an orifice in said circulation system on the suction side of said compressor during the heatin period of said circulation s stem for buil in up a back pressure on, t e compression side of said compressor for compensating the drop 1n compression pressure incident to the functiomng of said refrigerant as a heating medium 0 said coil and drainage means, for maintaining the heating efliciency of said compressor during said heating period.

4;. Defrosting refrigeration circulation system including a compressor and a refrigcrating coil, drainage means underlying said coil, said circulation s stem being divided lnto parallel branches between the pressure side of said compressor and said coil, one of said branches having a portion ar ranged in heat exchanging relation to said dralnage means, means for selectively determlning the path of flow of said refrigerant through one or the other of said branches, and a valve in said circulation system on the suction side of said compressor, adapted to be opened during the freezing c cle of said circulation system and closed durmg its heating cycle, said valve having an orifice providmg a throttled flow through the suction side of said circulation system when said valve is closed for building up a back pressure on the compression side of said compressor for compensating the drop in compression pressure incident to the functioning of said refrigerant as a heating medium of said coil and drainage means, for maintaining the heating efiiciency of said compressor during the heating period.

In testimony whereof I aifix my signature.

VIRGIL P. WARREN. 

